A general check on the availability of Macs mini, carried out by the AppleInsider, indicates that Apple may be preparing to launch a new model possibly with more advanced graphics chipsets (it says NVIDIA MCP89) and HDMI output, in place of the current DVI.
Over the past two weeks or so, inventory levels for the most basic Mac have been reduced considerably at stores / resellers in contact with the vehicle. When this happens, it is common for a new model to be arriving.
Although we are only a few days away from the beginning of WWDC 2010, the event is not usually the stage for such launches. In the case of the Mac mini, Apple is much more likely to launch the update “silently”, perhaps a week or two after the event.
The strongest rumor about a Mac mini with HDMI appeared in the beginning of March, raised by “safe sources” of the own AppleInsider.